Sheet separating/conveying mechanism and sheet conveying apparatus therewith

ABSTRACT

A sheet separating/conveying mechanism  30  has an upper unit  30   a  in which a paper feed roller  31  and other components are arranged and a lower unit  30   b  in which a separating roller  32,  an arm member  36,  and other components are arranged. The arm member  36  is U-shaped as seen in a plan view by being composed of a left and a right movable lever  36   a  that are mutually parallel and that make contact with both ends of a center shaft  23   b  and a pivot shaft  36   b  that supports the movable levers  36   a  so that they are rotatable in a direction indicated by arrow BB′. The movable levers  36   a  have locking holes  39  formed at the tip ends thereof, and the lower ends of tension springs  38  are locked in those locking holes  39.  The lower unit  30   b  is fitted with an applied force adjusting member  45  on which locking portions  42   a  and  42   b  are formed to protrude therefrom leftward and rightward that permit adjustment of the positions at which the upper ends of the tension springs  38  are locked.

This application is based on Japanese Patent Applications Nos.2005-141572 and 2005-141592, both filed on May 13, 2005, the contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet conveying apparatus that isused in an image forming apparatus such as a digital copier or laserprinter to convey sheets of copying paper or sheets of an originaldocument. More particularly, the present invention relates to a sheetseparating/conveying mechanism that separates and then conveys one sheetafter another from a stack of sheets.

2. Description of Related Art

The construction of a conventional image forming apparatus is shown inFIG. 9. In the image forming apparatus (for example, printer) 1, to forman image, a photoconductor drum 5 that rotates clockwise in the figureis uniformly charged by a charger unit 4, then an electrostatic latentimage is formed on the photoconductor drum 5 by a laser beam from anexposure unit (such as a laser scanning unit) 7 according to an originaldocument image data, and then a developer agent (hereinafter “toner”) isadhered to the electrostatic latent image by a developer unit 8 to forma toner image.

The toner is supplied to the developer unit 8 from a toner container 9.The image data is transmitted from a personal computer (unillustrated)or the like. In addition, a charge eliminating unit (unillustrated) foreliminating the residual charge on the surface of the photoconductordrum 5 is provided on the downstream side of the cleaning unit 18.

Toward the photoconductor drum 5 having the toner image formed thereonas described above, a sheet is conveyed from a paper feed cassette 10via a sheet conveying passage 11 and a pair of resist rollers 12, sothat the toner image formed on the surface of the photoconductor drum 5is transferred to the sheet by a transfer roller 13 (an image transferunit). The sheet having the toner image transferred thereto is thenseparated from the photoconductor drum 5, and is then conveyed to afixing unit 14 having a pair of fixing rollers 14 a, where the tonerimage is fixed. The sheet having passed through the fixing unit 14 isconveyed to an upper part of the apparatus via a sheet conveying passage15, and is then ejected into an ejected paper tray 17 by a pair ofejecting rollers 16.

Next, the construction of the paper feed cassette will be described.FIG. 10 is a side sectional view of the paper feed cassette 10. Sheets26 set in a cassette base 25 of the paper feed cassette 10 are pressedonto a pickup roller 29, which is provided in the main body of theapparatus, with a predetermined pressure exerted by a sheet mount plate28, which is loaded with an upward acting force applied by a conicalcompression spring 27. When a copy start button of the image formingapparatus is operated, the pickup roller 29 and a paper feed roller 31are driven to rotate in the directions indicated by arrows in FIG. 9.

Usually, one or a plurality of sheets among those located in a top partof the sheets 26 set on the sheet mount plate 28 are fed by the pickuproller 29 to a sheet separating/conveying mechanism 30, which has thepaper feed roller 31 and a separating roller 32. If a plurality ofsheets are fed to the nip between the paper feed roller 31 and theseparating roller 32, only the topmost one of the sheets is separated bythe separating roller 32 so as to be conveyed toward the sheet conveyingpassage 11. Here, the rotation of the separating roller 32 is controlledby a torque limiter (see FIG. 12) so that the separating roller 32either remains at rest or rotates in the same direction as the paperfeed roller 31. A rear-edge cursor 33 for truing up the rear edges ofthe sheets 26 is provided so as to be movable in the sheet conveyingdirection (left/right direction).

FIG. 11 is an enlarged view of the sheet separating/conveying mechanism30 shown in FIG. 10, and FIG. 12 is a front view as seen from thedirection indicated by arrow C in FIG. 11. The sheetseparating/conveying mechanism 30 is composed of: an upper unit 30 a inwhich the paper feed roller 31 and other components are arranged andthat forms an upper guide for the conveyed sheet; and a lower unit 30 bin which the separating roller 32, an arm member 36, and othercomponents are arranged and that forms a lower guide for the conveyedsheet.

The separating roller 32 is composed of: a roller body 32 a formed of anelastic material; and a center shaft 32 b that penetrates the center ofrotation of the roller body 32 a. At each end of the center shaft 32 bin the axial direction thereof, a bracket 34 is fixed, and a guidegroove 35 that engages with the bracket 34 is formed in the cassettebase 25 (see FIG. 10). Thus, the separating roller 32 is supported so asto be slidable along the guide groove 35 in the directions indicated byarrows AA′. Moreover, the separating roller 32 is fitted with a torquelimiter 41 so that the roller body 32 a rotates only when it receives adriving force stronger than a predetermined level.

The arm member 36 is formed in a substantially rectangular shape bybeing composed of: two mutually parallel movable levers 36 a each makingcontact with one end of the center shaft 32 b; and a pivot shaft 36 band a linking portion 36 c that link together the movable levers 36 a.The arm member 36 is supported by the pivot shaft 36 b so as to berotatable in the directions indicated by arrows BB′. It should be notedthat, in FIG. 11, only the movable lever 36 a on one side is shown. In amiddle part of the linking portion 36 c in the length direction thereof,a locking hole 39 is formed in which one end of a tension spring 38 islocked. The other end of the tension spring 38 is locked to a lockingportion (unillustrated) of the lower unit 30 b. Thus, the arm member 36is loaded by the tension spring 38 with a force acting in the directionindicated by arrow B so that, in a middle part of the movable levers 36a, the arm member 36 applies to the center shaft 32 b a pressure actingin the direction indicated by arrow B.

A retraction projection 43 is formed on the pivot shaft 36 b of the armmember 36. When the paper feed cassette 10 (see FIG. 10) is pulled outin the direction (indicated by arrow D) perpendicular to the sheetconveying direction, the retraction projection 43 rides on an elevation44 formed on the floor face of the apparatus to rotate the arm member 36in the direction indicated by arrow B′. That is, at the same time thatthe paper feed cassette 10 is pulled out of the main body of theapparatus, the separating roller 32 moves apart from the paper feedroller 31. Thus, even if a sheet is caught in the nip between the paperfeed roller 31 and the separating roller 32, the sheet is prevented frombreaking.

In the sheet separating/conveying mechanism described above, to ensurethat a single sheet is separated without fail even if more than onesheet is fed simultaneously, as disclosed in JP-A-2004-026479, theseparating roller 32 is pressed onto the paper feed roller 31 with apredetermined pressure by force applying means such as the tensionspring 38. Here, the pressure with which the separating roller 32 isoptimally pressed onto the paper feed roller 31 varies with thethickness of the sheet actually used and other factors. Thus, forexample, if the pressure is too strong, a plurality of sheets are fedsimultaneously and, of the pressure is too weak, no sheet at all is fed,in either case resulting in a paper feed error. On the other hand, ifthe pressure is uneven at the left and right sides of the separatingroller 32 in the axial direction thereof, the sheet is conveyedobliquely or otherwise in an undesired way.

Under these circumstances, there have been proposed various methods foradjusting the pressure with which a separating member such as aseparating roller is pressed onto a paper feed roller. For example,JP-A-2001-031275 discloses a sheet separating/conveying mechanismprovided with pressing force adjusting means for adjusting the pressingforce with which pressing means (a spring) presses a separating rolleronto a paper feed roller wherein the pressing force with which theseparating roller is pressed can be adjusted by varying the length of aspring with a tool such as a screwdriver.

However, in the construction shown in FIG. 11, whereas the separatingroller 32 slides linearly in the direction (indicated by arrows AA′)perpendicular to the sheet conveying direction, the movable levers 36 a,which presses the separating roller 32, moves circularly about the pivotshaft 36 b. That is, the direction in which the pressing force from themovable levers 36 a is transmitted does not coincide with the directionin which the separating roller 32 slides, and thus friction occurs atthe contact between the center shaft 32 b and the movable levers 36 aand between the center shaft 32 b and the side walls of the guide groove35. This hampers smooth transmission of the force applied by the tensionspring 38 to the separating roller 32.

On the other hand, JP-A-H10-207141, which is directed to a paperpost-processing apparatus that nips and conveys one sheet of recordingmaterial after another at the nip formed between two rollers kept incontact with each other while “de-curling” (flattening) curled sheets,discloses a method for adjusting the intensity of de-curling stepwise byvarying the axis-to-axis distance between the rollers stepwise.

Moreover, JP-A-2002-302324, which is directed to an original documentfeeding apparatus that conveys one sheet after another by the use of aseparating roller and a separating belt, discloses a method foradjusting the pressure without replacement of components but instead bymanipulating a positioning member for adjusting the distance between theseparating roller and the separating belt by the use of an adjustmentscale provided along the displacement direction of the positioningmember. Inconveniently, however, with the methods disclosed inJP-A-H10-207141 and JP-A-2002-302324, it is difficult to recognize at afirst glance in which direction to adjust. This may lead to an undulylong time required in the assembly of the apparatus and in readjustmentby a serviceperson, and to adjustment errors.

Moreover, in a case where, as shown in FIG. 12, the roller body 32 a isarranged not in the middle of the center shaft 32 b but slightlyleftward, the force applied at the left and right sides of the rollerbody 32 a needs to be made even by applying a stronger force at the leftside, where the distance from the roller body 32 a to the end of thecenter shaft 32 b is shorter, than at the right side by exploiting theprinciple of a lever. On the other hand, in a case where the torquelimiter 41 is arranged on the right side of the roller body 32 a, thecenter of gravity of the separating roller 32 is located not in themiddle thereof but slightly rightward. This requires that the force beapplied so much more at the right side as the center of gravity isdisplaced. In this way, it is necessary to adjust the force applied atthe left and right sides in the axial direction separately withconsideration given to the arrangement of the separating roller 32 andthe displacement of the center of gravity attributable to the torquelimiter 41.

Inconveniently, however, with the construction shown in FIG. 12, sincethe tension spring 38 is linked to one location in a middle part of theseparating roller 32 in the axial direction, it is impossible to adjustthe force applied at the left and right sides independently.Incidentally, although the above description deals with a paper feedcassette incorporated in an image forming apparatus to serve as a sheetpaper feeding source, the same inconveniences are experienced in anoriginal document conveying apparatus (ADF—automatic document feeder)that automatically conveys sheets of an original document or a paperfeeding apparatus that is used as an interleaf paper feeding source.

SUMMARY OF THE INVENTION

In view of the conventionally experienced inconveniences mentionedabove, it is an object of the present invention to provide a sheetseparating/conveying mechanism that permits the force with which aseparating member such as a separating roller is pressed to be adjustedeasily and independently at the left and right sides thereof in theaxial direction, and to provide a sheet conveying apparatus providedwith such a sheet separating/conveying mechanism. It is another objectof the present invention to easily and inexpensively provide a sheetseparating/conveying mechanism that permits smooth transmission of aforce from force applying means so that a separating member such as aseparating roller is pressed with a stable pressure, and to provide asheet conveying apparatus provided with such a sheetseparating/conveying mechanism.

To achieve the above objects, according to one aspect of the presentinvention, a sheet separating/conveying mechanism that is provided witha paper feed roller for feeding a sheet in the sheet conveyingdirection, a separating member pressed onto a lower part of the paperfeed roller or taken away therefrom in the direction approximatelyperpendicular to the sheet conveying direction, and force applying meansfor pressing the separating member onto the paper feed roller and thatseparates and conveys only the topmost sheet from a stack of sheets ischaracterized in that the force applying means permits the applied forceto be adjusted independently at both sides of the separating member inthe axial direction thereof.

With this construction, the pressure with which the separating member ispressed onto the paper feed roller can be adjusted separately at theleft and right sides in the axial direction. This permits the separatingmember to be pressed more evenly at the left and right sides than isconventionally possible. Thus, it is possible to effectively reduceoblique sheet feeding and improper paper feeding.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the force applying meansincludes two tension springs that apply the force to both sides of theseparating member in the axial direction thereof and an applied forceadjusting member that is provided with, one at each of the left andright sides thereof, locking portions for locking one ends of thetension springs. Here, the locking portions each have a plurality ofengagement grooves formed therein at different positions in thedirection of expansion/contraction of the tension springs.

With this construction, the applied force can be easily adjusted bychanging the engagement positions of the tension springs according tothe displacement of the center of gravity of the separating member, thethickness of sheets actually used, and other factors.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the engagement grooves areformed stepwise along the upper edges of the locking portions, and aflexible sheet member is attached above the locking portions so as toclose the open ends of the engagement grooves. The sheet member isretractable to a position where it leaves open the open ends.

With this construction, there is no risk of the tension springsdisengaging from the engagement grooves while a sheet is being conveyed.On the other hand, when the applied force is readjusted, the sheetmember can be bent to leave open the open ends of the engagementgrooves, so that the engagement positions of the tension springs can beeasily adjusted.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, on the applied force adjustingmember, for each of the locking portions, as many marking symbols as theengagement grooves formed therein are provided.

With this construction, by previously marking the marking symbols thatcorrespond to the initially adjusted positions of the tension springs,it is possible to enhance work efficiency in the assembly andreadjustment of the apparatus, and also to reduce adjustment errors.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the marking symbols areprovided to correspond to the arrangement of the engagement grooves.

With this construction, the adjusted positions of the tension springscan be grasped at a glance in the assembly and readjustment of theapparatus.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the separating member is aseparating roller composed of a roller body formed of an elasticmaterial and a center shaft that penetrates the center of rotation ofthe roller body.

With this construction, the force applied to the separating roller canbe adjusted separately at the left and right sides so that the pressurewith which the separating roller is pressed onto the paper feed rolleris even in the axial direction.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the separating roller isprovided with a torque limiter that permits the roller body to rotateonly when a driving force stronger than a predetermined level isapplied.

With this construction, by controlling the rotation of the separatingroller with the torque limiter, it is possible to further enhance thesheet separation performance, and thereby to reduce paper feed errorssuch as multiple sheets being fed simultaneously or no sheet being fedat all.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, in the locking portions,mutually corresponding ones of the engagement grooves are formed, withconsideration given to the arrangement of the roller body in the axialdirection thereof and the position of the center of gravity of theseparating roller, in such positions that the force applied by thetension springs acts equally at the left and right sides of the rollerbody.

With this construction, simply by engaging the left and right tensionsprings with the engagement grooves located to correspond to each other,it is possible to make the applied force act evenly at the left andright sides of the roller body irrespective of the arrangement of theroller body or the position of the center of gravity of the separatingroller.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the force applying means hasmovable levers that are rotatably supported at one ends thereof and thathave the tension springs coupled to the other ends thereof, so that themovable levers apply the force applied by the tension springs to theseparating member by making contact therewith, and rotary followermembers are provided in the parts of the separating member where itmakes contact with the movable levers.

With this construction, it is possible to reduce friction in the partsof the separating member and the movable levers where they make contactwith each other. Thus, it is possible to press the separating memberonto and take it away from the paper feed roller smoothly.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the separating member is aseparating roller composed of a roller body formed of an elasticmaterial and a center shaft that penetrates the center of rotation ofthe roller body, and the rotary follower members are fitted at both endsof the center shaft.

With this construction, it is possible to reduce friction at both endsof the separating roller. Thus, it is possible to apply the appliedforce to the separating roller smoothly, and to make even the force withwhich the separating roller is pressed onto the paper feed roller in theaxial direction.

According to the present invention, in the sheet separating/conveyingmechanism constructed as described above, the rotary follower membersare bearings.

With this construction, it is possible to more effectively reducefriction between the separating member and the movable levers, andthereby to press the separating member onto and take it away from thepaper feed roller more smoothly.

According to another aspect of the present invention, a sheet conveyingapparatus is provided with the sheet separating/conveying mechanismconstructed as described above.

With this construction, it is possible to easily and inexpensivelyrealize a sheet conveying apparatus in which a force is applied to theseparating member evenly in the axial direction thereof to permit theseparating member to be pressed onto and taken away from the paper feedroller smoothly so as to reduce oblique sheet feeding and improper paperfeeding and to permit easy adjustment of the applied force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing the construction of the sheetseparating/conveying mechanism of a first embodiment of the presentinvention;

FIG. 2 is a perspective view of the lower unit of the sheetseparating/conveying mechanism of the first embodiment, as seen fromwhere the applied force adjusting member is located;

FIG. 3 is a perspective view of the applied force adjusting member usedin the sheet separating/conveying mechanism of the first embodiment;

FIG. 4 is an enlarged view of a part around a locking portion of theapplied force adjusting member;

FIG. 5 is an enlarged view showing another construction around thelocking portion;

FIG. 6 is a side view showing the construction of the sheetseparating/conveying mechanism of a second embodiment of the presentinvention;

FIG. 7 is a front view showing the construction of the sheetseparating/conveying mechanism of the second embodiment;

FIGS. 8 a and 8 b are side views illustrating how a force is applied tothe separating roller via the movable levers in the sheetseparating/conveying mechanism of the second embodiment;

FIG. 9 is a sectional view showing an outline of the overallconstruction of a conventional image forming apparatus;

FIG. 10 is a side sectional view showing the construction of aconventional paper feed cassette;

FIG. 11 is a side view showing a conventional sheet separating/conveyingmechanism, and

FIG. 12 is a front view showing the conventional sheetseparating/conveying mechanism.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. FIG. 1 is a front view showingthe construction of a sheet separating/conveying mechanism of a firstembodiment of the present invention. Such parts as are found also in theconventional example shown in FIG. 12 are identified with commonreference numerals, and no description thereof will be repeated. In thisembodiment, the arm member 36 is U-shaped as seen in a plan view bybeing composed of two mutually parallel movable levers 36 a that makecontact with both ends of the center shaft 32 b and a pivot shaft 36 bthat links together the movable levers 36 a.

The left and right movable levers 36 a have locking holes 39 formed atthe tip ends thereof, and the lower ends of tension springs 38 arelocked in those locking holes 39. The upper ends of the tension springs38 are locked on locking portions 42 a and 42 b, respectively, of anapplied force adjusting member (described later) fitted to the lowerunit 30 b (see FIG. 11).

With this construction, the pressure with which the separating roller 32is pressed onto the paper feed roller 31 can be adjusted separately atthe left and right sides in the direction of the center shaft 32 b.Thus, as compared with the conventional construction in which a force isapplied with a single tension spring 38, a force can be applied to theroller body 32 a more evenly at the left and right sides. This helpseffectively reduce oblique sheet feeding and improper paper feeding.

FIG. 2 is a perspective view of the lower unit 30 b as seen from thebottom of FIG. 1. Reference numeral 45 represents an applied forceadjusting member that permits adjustment of the force applied by theleft and right tension springs 38. The applied force adjusting member 45is fixed to the lower unit 30 b with screws. At the left and right endsof the applied force adjusting member 45, locking portions 42 a and 42 bare formed to protrude therefrom. The locking portions 42 a and 42 bpermit adjustment of the locking positions of the tension springs 38.

The structure of the applied force adjusting member 45 is shown in FIG.3. The applied force adjusting member 45 is a metal plate that has avertical surface 45 a and a horizontal surface 45 b and that issubstantially L-shaped in a cross section thereof. The locking portions42 a and 42 b are formed to protrude obliquely upward from the left andright ends of the vertical surface 45 a. In the horizontal surface 45 b,screw holes 46 are formed that permit the applied force adjusting member45 to be fixed to the lower unit 30 b (see FIG. 2).

Moreover, on the vertical surface 45 a, as many marking symbols 47(here, seven at each of the left and right sides) are impressed as thereare formed engagement grooves (described later) in the locking portions42 a and 42 b. By previously marking the marking symbols 47 thatcorrespond to the initial adjustment positions of the tension springs38, the adjustment positions of the tension springs 38 can be grasped ata glance in the assembly of the apparatus. This helps enhance workefficiency and reduce adjustment errors.

The optimal value of the force applied by the tension springs 38 variesaccording to the thickness of the sheet actually used. In the assemblyof the apparatus, the applied force is set at an optimal value thatcorresponds to the thickness of standard sheets. However, in a casewhere frequently used sheets are not standard sheets, a user orserviceperson readjusts the applied force to suit the thickness of thosesheets. Even in this case, the marking positions of the marking symbols47 can be referred to to move, by the desired positions, the lockingpositions of the tension springs 38 from the initial adjustmentpositions. This makes readjustment easy.

FIG. 4 is an enlarged view of a part around the locking portion 42 b(the part inside circle S shown in FIG. 3). The locking portion 42 b hasseven engagement grooves 48 formed therein stepwise at differentpositions in the direction of the expansion/contraction of the tensionsprings 38 (in the up/down direction of the figure). For example, in acase where the fourth marking symbol 47 (see FIG. 3) is marked as theinitial adjustment position, as shown in FIG. 4, the tension spring 38is locked in the fourth engagement groove 48 as counted from inside.

The locking portion 42 a is similarly structured, and therefore noseparate description will be given thereof. It should be noted, however,that the locking portions 42 a and 42 b are not symmetrical, but are sodesigned that even a pair of engagement grooves 48 located at mutuallycorresponding positions makes the tension springs 38 expand to differentlengths, that is, make them exert different forces. As shown in FIG. 1,the roller body 32 a of the separating roller 32 is arranged not in themiddle of the center shaft 32 b but slightly leftward. Thus, to make theforce applied to the left and right sides of the roller body 32 a even,it is necessary, by the principle of a lever, to apply a stronger forceat the left side, where the distance from the roller body 32 a to theend of the center shaft 32 b is shorter, than at the right side.

On the other hand, since the torque limiter 41 is arranged on the rightside of the separating roller 32, the center of gravity of theseparating roller 32 is located not in the middle thereof in the axialdirection but slightly rightward. Thus, the force applied at the rightside needs to be made so much stronger as the center of gravity isdisplaced. Accordingly, the left and right locking portions 42 a and 42b have their engagement grooves 48 formed in positions determined withconsideration given to the arrangement of the separating roller 32 andthe displacement of the center of gravity attributable to the torquelimiter 41. Thus, when the tension springs 38 are locked in a pair ofengagement grooves 48 at mutually corresponding positions in the lockingportions 42 a and 42 b, the applied force acts evenly at the left andright sides of the roller body 32 a.

In a case where the engagement grooves 48 are formed stepwise as shownin FIG. 4, when the paper feed cassette 10 is removed and inserted, aswinging movement of the movable levers 36 a may cause the tensionsprings 38 to disengage from the engagement grooves 48. To prevent this,as shown in FIG. 5, flexible sheet members 50 are attached above thelocking portions 42 a and 42 b, with only a fixing portion 50 a of thesheet member 50 fixed with adhesive, so that a flexible portion 50 bthereof, at the bottom edge thereof, closes the open ends of theengagement grooves 48. This prevents a swinging movement of the movablelevers 36 a from causing the tension springs 38 to disengage from theengagement grooves 48. Moreover, when the applied force is readjusted,by bending the flexible portion 50 b toward the face of sheets to openthe open ends of the engagement grooves 48, it is possible to easilyadjust the engagement positions of the tension springs 38.

The sheet member 50 may be formed of any material so long as it isformed as a flexible sheet of synthetic resin or the like. It is,however, preferable that the sheet be so strong as to keep the tensionsprings 38 engaged. A preferred example of the sheet is a sheet (Lumilarsheet) of polyethylene terephthalate (PET).

The shapes and arrangement of the applied force adjusting member 45, thelocking portions 42 a and 42 b, and the engagement grooves 48specifically described above are merely an example thereof, and may bemodified as necessary to suit the specifications of the sheetseparating/conveying mechanism 30. For example, instead of the lockingportions 42 a and 42 b being formed to protrude, the engagement grooves48 may be formed along the left and right edges of the vertical surface45 a. In this case, forming the engagement grooves 48 hook-shapedprevents the tension springs 38 from disengaging therefrom even withoutthe provision of the sheet member 50.

FIG. 6 is a side view showing the construction of the sheetseparating/conveying mechanism of a second embodiment of the presentinvention, and FIG. 7 is a front view thereof as seen from the directionindicated by arrow C in FIG. 6. Such parts as are found also in FIG. 11or in FIG. 1, which shows the first embodiment, are identified withcommon reference numerals, and no description thereof will be repeated.In this embodiment, at both ends of the center shaft 32 b of theseparating roller 32, bearings 40 are fitted. The separating roller 32is so built as to make contact with the movable levers 36 a via thebearings 40. In FIG. 7, the tension spring 38 at the right side isomitted.

Thus, in a state where the separating roller 32 is located apart fromthe paper feed roller 31, when the arm member 36 rotates in thedirection indicated by arrow B under the force applied thereto by thetension springs 38, as shown in FIG. 8 a, the movable levers 36 a givesthe center shaft 32 b a pressing force that acts in the directionindicated by arrow B. Here, the bearings 40 fitted around the centershaft 32 b rotate in the direction indicated by arrow C, and thus thecenter shaft 32 b slides in the direction indicated by arrow A along theguide grooves 35 (see FIG. 6).

On the other hand, in a state where the separating roller 32 is pressedonto the paper feed roller 31, when the arm member 36 rotates in thedirection indicated by arrow B′ against the force applied by the tensionsprings 38, as shown in FIG. 8 b, the bearings 40 rotate in thedirection indicated by arrow C′ to follow the movable levers 36 aretracting in the direction indicated by arrow B′, and thus the centershaft 32 b slides in the direction indicated by arrow A′. Accordingly,no friction occurs at the contact between the center shaft 32 b and themovable levers 36 a or between the center shaft 32 b and the guidegrooves 35. Thus, with the movable levers 36 a, the separating roller 32can be slid smoothly in the direction indicated by arrows AA′.

In this embodiment, the bearings 40 are fitted on the center shaft 32 bto permit the separating roller 32 to slide smoothly. Instead of thebearings 40, any other rotary follower members such as rollers may befitted that can freely rotate relative to the center shaft 32 b. Therotary follower members may be formed of metal, resin, or any othermaterial.

In any other aspects, the present invention may be carried out in anyother manners than specifically described above, and many modificationsand variations are possible within the spirit of the present invention.For example, in the embodiments described above, instead of using thesubstantially U-shaped arm member 36 to give the separating roller 32its pressing force, the pivot shaft 36 b may be provided one at each ofthe left and right sides independently so that the movable levers 36 aare supported separately. Instead of the tension springs 38, any othertype of spring member may be used, such as compression springs, torsionsprings, or plate springs.

The embodiments described above deal with a sheet separating/conveyingmechanism that prevents multiple feeding of sheets by pressing aseparating roller 32 onto a paper feed roller 31. These constructions,however, are equally applicable to a sheet separating/conveyingmechanism in which, instead of the separating roller 32, a separatingpad or separating belt formed of an elastic material is pressed onto thepaper feed roller 31.

The embodiments described above deal with examples in which a sheetseparating/conveying mechanism is incorporated in a paper feed cassette10 that is incorporated as a sheet paper feeding source in an imageforming apparatus. The sheet separating/conveying mechanism, however,may also be applied to an ADF that automatically conveys sheets of anoriginal document or a paper feeding apparatus that is used as aninterleaf paper feeding source.

According to the present invention, it is possible to adjust the forceapplied to a separating member separately at the left and right sides inthe axial direction. Thus, it is possible to realize a sheetseparating/conveying mechanism that can press a separating member onto apaper feed roller with a pressure more even at the left and right sidesthan is conventionally possible and that can thus effectively preventoblique sheet feeding and improper paper feeding.

Moreover, force applying means is used that includes two tension springsand an applied force adjusting member having locking portions formed attwo, left and right, locations, each locking portion having a pluralityof engagement grooves, with which the tension springs are to be engaged,formed at different positions in the direction of theexpansion/contraction of the springs. Thus, it is possible to easilyadjust the force applied by the tension springs to suit the displacementof the center of gravity of the separating member, the thickness of thesheet actually used, and other factors.

Moreover, the engagement grooves are formed stepwise along the upperedges of the locking portions, and, above the locking portions, aflexible sheet member is attached to close the open ends of theengagement grooves. This prevents, when a sheet is being conveyed, thetension springs from disengaging from the engagement grooves. When theapplied force is readjusted, the sheet member is bent so as to beretracted to a position where it leaves open the open ends of theengagement grooves. This permits easy adjustment of the engagementpositions of the tension springs.

Moreover, for each locking portion, as many marking symbols are providedin the applied force adjusting member as there are formed engagementgrooves. Thus, by previously marking the marking symbols correspondingto the initial adjustment positions of the tension springs, it ispossible to enhance work efficiency and reduce adjustment errors in theassembly or the readjustment of the apparatus. Furthermore, by makingthe arrangement of the marking symbols correspond to the arrangement ofthe engagement grooves, it is possible to grasp the adjustment positionsof the tension springs at a glance.

Moreover, the separating member is built as a separating roller composedof a roller body and a center shaft, and the engagement grooves areformed in the locking portions with consideration given to thearrangement of the roller body in the axial direction and the positionof the center of gravity of the separating roller. Thus, simply byengaging the tension springs with a pair of engagement grooves locatedat corresponding positions at the left and right sides, it is possibleto apply a force to the roller body evenly at the left and right sides.

Moreover, in a case where the force is applied via the movable levers tothe separating member, providing rotary follower members at the contactbetween the separating member and the movable levers helps, as a resultof the rotary follower members rotating, prevent friction at the contactbetween the movable levers and the separating member. Thus, through therotation of the movable levers, the force applied to the separatingmember is converted into a force acting in the direction in which theseparating member slides, and thereby permits the separating member toslide smoothly.

Moreover, by incorporating a sheet separating/conveying mechanismaccording to the present invention in a sheet conveying apparatus suchas a paper feed cassette or original document conveying apparatus, it ispossible to realize a sheet conveying apparatus in which the forceapplied to a separating member is made even in the axial direction toreduce oblique sheet feeding and improper paper feeding and to permiteasy adjustment of the applied force.

1. A sheet separating/conveying mechanism comprising: a paper feedroller for feeding a sheet in a sheet conveying direction; a separatingmember pressed onto a lower part of said paper feed roller or taken awaytherefrom in a direction approximately perpendicular to the sheetconveying direction; and force applying means for pressing saidseparating member onto said paper feed roller, said force applying meanspermitting an applied force to be adjusted independently at both sidesof said separating member in an axial direction thereof, wherein saidsheet separating/conveying mechanism separates and conveys only atopmost sheet from a stack of sheets.
 2. The sheet separating/conveyingmechanism of claim 1, wherein said force applying means includes: twotension springs that apply the force to both sides of said separatingmember in the axial direction thereof; and an applied force adjustingmember provided with, one at each of left and right sides thereof,locking portions for locking one ends of the tension springs, whereinsaid locking portions each have a plurality of engagement grooves formedtherein at different positions in a direction of expansion/contractionof said tension springs.
 3. The sheet separating/conveying mechanism ofclaim 2, wherein said engagement grooves are formed stepwise along upperedges of said locking portions, and a flexible sheet member is attachedabove said locking portions so as to close open ends of said engagementgrooves, said sheet member being retractable to a position where saidsheet member leaves open the open ends.
 4. The sheetseparating/conveying mechanism of claim 2, wherein, on said appliedforce adjusting member, for each of said locking portions, as manymarking symbols as said engagement grooves formed therein are provided.5. The sheet separating/conveying mechanism of claim 3, wherein, on saidapplied force adjusting member, for each of said locking portions, asmany marking symbols as said engagement grooves formed therein areprovided.
 6. The sheet separating/conveying mechanism of claim 4,wherein said marking symbols are provided to correspond to arrangementof said engagement grooves.
 7. The sheet separating/conveying mechanismof claim 5, wherein said marking symbols are provided to correspond toarrangement of said engagement grooves.
 8. The sheetseparating/conveying mechanism of claim 1, wherein said separatingmember is a separating roller composed of a roller body formed of anelastic material and a center shaft that penetrates a center of rotationof the roller body.
 9. The sheet separating/conveying mechanism of claim8, wherein said separating roller is provided with a torque limiter thatpermits said roller body to rotate only when a driving force strongerthan a predetermined level is applied.
 10. The sheetseparating/conveying mechanism of claim 8, wherein, in said lockingportions, mutually corresponding ones of said engagement grooves areformed, with consideration given to arrangement of said roller body inan axial direction thereof and a position of a center of gravity of saidseparating roller, in such positions that the force applied by thetension springs acts equally at left and right sides of said rollerbody.
 11. The sheet separating/conveying mechanism of claim 9, wherein,in said locking portions, mutually corresponding ones of said engagementgrooves are formed, with consideration given to arrangement of saidroller body in an axial direction thereof and a position of a center ofgravity of said separating roller, in such positions that the forceapplied by the tension springs acts equally at left and right sides ofsaid roller body.
 12. The sheet separating/conveying mechanism of claim1, wherein said force applying means has movable levers that arerotatably supported at one ends thereof and that have said tensionsprings coupled to the other ends thereof, so that said movable leversapply the force applied by the tension springs to said separating memberby making contact therewith, and rotary follower members are provided inparts of said separating member where said separating member makescontact with said movable levers.
 13. The sheet separating/conveyingmechanism of claim 12, wherein said separating member is a separatingroller composed of a roller body formed of an elastic material and acenter shaft that penetrates a center of rotation of the roller body,and said rotary follower members are fitted at both ends of said centershaft.
 14. The sheet separating/conveying mechanism of claim 13, whereinsaid rotary follower members are bearings.
 15. A sheet conveyingapparatus comprising the sheet separating/conveying mechanism of claim1.